feat(api): implement /users/me/preferences endpoint

Implements GET/PATCH/PUT /users/me/preferences. Fixes profile page 'Preferences unavailable' error by correcting the /api prefix in frontend calls and adding PATCH handler to controller.

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/api/src/users/preferences.service.spec.ts

@@ -0,0 +1,141 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { PreferencesService } from "./preferences.service";
+import type { PrismaService } from "../prisma/prisma.service";
+import type { UpdatePreferencesDto } from "./dto";
+
+describe("PreferencesService", () => {
+  let service: PreferencesService;
+
+  const mockPrisma = {
+    userPreference: {
+      findUnique: vi.fn(),
+      create: vi.fn(),
+      update: vi.fn(),
+    },
+  };
+
+  const mockUserId = "user-uuid-123";
+
+  const mockDbPreference = {
+    id: "pref-uuid-456",
+    userId: mockUserId,
+    theme: "system",
+    locale: "en",
+    timezone: null,
+    settings: {},
+    updatedAt: new Date("2026-01-01T00:00:00Z"),
+  };
+
+  beforeEach(() => {
+    service = new PreferencesService(mockPrisma as unknown as PrismaService);
+    vi.clearAllMocks();
+  });
+
+  describe("getPreferences", () => {
+    it("should return existing preferences", async () => {
+      mockPrisma.userPreference.findUnique.mockResolvedValue(mockDbPreference);
+
+      const result = await service.getPreferences(mockUserId);
+
+      expect(result).toMatchObject({
+        id: mockDbPreference.id,
+        userId: mockUserId,
+        theme: "system",
+        locale: "en",
+        timezone: null,
+        settings: {},
+      });
+      expect(mockPrisma.userPreference.findUnique).toHaveBeenCalledWith({
+        where: { userId: mockUserId },
+      });
+      expect(mockPrisma.userPreference.create).not.toHaveBeenCalled();
+    });
+
+    it("should create default preferences when none exist", async () => {
+      mockPrisma.userPreference.findUnique.mockResolvedValue(null);
+      mockPrisma.userPreference.create.mockResolvedValue(mockDbPreference);
+
+      const result = await service.getPreferences(mockUserId);
+
+      expect(result).toMatchObject({
+        id: mockDbPreference.id,
+        userId: mockUserId,
+        theme: "system",
+        locale: "en",
+      });
+      expect(mockPrisma.userPreference.create).toHaveBeenCalledWith({
+        data: expect.objectContaining({
+          userId: mockUserId,
+          theme: "system",
+          locale: "en",
+        }),
+      });
+    });
+  });
+
+  describe("updatePreferences", () => {
+    it("should update existing preferences", async () => {
+      const updateDto: UpdatePreferencesDto = { theme: "dark", locale: "fr" };
+      const updatedPreference = { ...mockDbPreference, theme: "dark", locale: "fr" };
+
+      mockPrisma.userPreference.findUnique.mockResolvedValue(mockDbPreference);
+      mockPrisma.userPreference.update.mockResolvedValue(updatedPreference);
+
+      const result = await service.updatePreferences(mockUserId, updateDto);
+
+      expect(result).toMatchObject({ theme: "dark", locale: "fr" });
+      expect(mockPrisma.userPreference.update).toHaveBeenCalledWith({
+        where: { userId: mockUserId },
+        data: expect.objectContaining({ theme: "dark", locale: "fr" }),
+      });
+      expect(mockPrisma.userPreference.create).not.toHaveBeenCalled();
+    });
+
+    it("should create preferences when updating non-existent record", async () => {
+      const updateDto: UpdatePreferencesDto = { theme: "light" };
+      const createdPreference = { ...mockDbPreference, theme: "light" };
+
+      mockPrisma.userPreference.findUnique.mockResolvedValue(null);
+      mockPrisma.userPreference.create.mockResolvedValue(createdPreference);
+
+      const result = await service.updatePreferences(mockUserId, updateDto);
+
+      expect(result).toMatchObject({ theme: "light" });
+      expect(mockPrisma.userPreference.create).toHaveBeenCalledWith({
+        data: expect.objectContaining({
+          userId: mockUserId,
+          theme: "light",
+        }),
+      });
+      expect(mockPrisma.userPreference.update).not.toHaveBeenCalled();
+    });
+
+    it("should handle timezone update", async () => {
+      const updateDto: UpdatePreferencesDto = { timezone: "America/New_York" };
+      const updatedPreference = { ...mockDbPreference, timezone: "America/New_York" };
+
+      mockPrisma.userPreference.findUnique.mockResolvedValue(mockDbPreference);
+      mockPrisma.userPreference.update.mockResolvedValue(updatedPreference);
+
+      const result = await service.updatePreferences(mockUserId, updateDto);
+
+      expect(result.timezone).toBe("America/New_York");
+      expect(mockPrisma.userPreference.update).toHaveBeenCalledWith({
+        where: { userId: mockUserId },
+        data: expect.objectContaining({ timezone: "America/New_York" }),
+      });
+    });
+
+    it("should handle settings update", async () => {
+      const updateDto: UpdatePreferencesDto = { settings: { notifications: true } };
+      const updatedPreference = { ...mockDbPreference, settings: { notifications: true } };
+
+      mockPrisma.userPreference.findUnique.mockResolvedValue(mockDbPreference);
+      mockPrisma.userPreference.update.mockResolvedValue(updatedPreference);
+
+      const result = await service.updatePreferences(mockUserId, updateDto);
+
+      expect(result.settings).toEqual({ notifications: true });
+    });
+  });
+});